Fuel, such as jet fuel, diesel fuel and the like is seriously impaired if water becomes admixed with it. That is, most uses of fuel such as jet fuel, diesel fuel and so forth, such as in internal combustion engines, are very seriously affected by the presence of water in the fuel. First, of course, water is not combustible, and therefore, subtracts from the energy value available from a given quantity of fuel. Second, water freezes easily and can block fuel lines in cold environments. Third, water tends to carry with it contaminants and more readily reacts with metals to form rust. For these and other reasons, it is very important that in order to preserve high fuel quality water be prevented from traveling in a fuel flow system.
A known expedient to intercept water in a fuel system is to provide a filter media of the type which permits fuel, such as jet fuel, diesel fuel or the like, to pass therethrough but which resists the passage of water. Filters of this type include hydrophilic materials which absorb and expand in the presence of water, but which are not olefinic, that is, which do not absorb hydrocarbons. This type of filter media is useful in blocking the flow of water since the absorption and expansion can serve to close the filter media against the passage of fluid therethrough.
The use of a water absorbent filter media alone as a means of preventing the passage of water in a fuel flow system, however, is not sufficiently dependable. Instead, it is highly desirable that in a fuel flow filtering system a positive shutoff be provided so that when sufficient water is detected in a fuel flow system, such as by water absorbent fuel media swelling or otherwise reacting to resist the further fluid flow therethrough, a positive, mechanical type shutoff be obtained. U.S. Pat. No. 4,485,011 to Cole et al discloses a type of shutoff valve in conjunction with a fuel filter arrangement. In the device of the Cole et al patent a ball is maintained in a rest position as long as the pressure drop across a filter media is below a certain level, but is displaced when the pressure drop increases, such as occurs when the filter media absorbs water. The displaced ball is then passed to a valve closure position to stop further fluid flow through the filter.
The present disclosure is directed towards an improvement in the basic concept of Cole et al U.S. Pat. No. 4,485,011. More particularly, this disclosure provides a structure for controlling the position of a shutoff ball within a fuel filter. Therefore, this disclosure provides a fuel filter having improved means of preventing water and particulate contaminant from passing therethrough.
The filter includes an open end for effluent fuel through flow and a closed end with a bored pressure port sealed by a valve ball. A rigid, tubular, fluid pervious member formed of a stiff plastic and made up of radial and longitudinal ribs is positioned within the filter. The tubular member is affixed in sealed relationship to opposed first and second end caps that are each formed of an injection molded fiber glass/plastic compound. The second end cap is affixed in a manner so as to provide closed communication with a fuel outlet opening in a cartridge plate of a pressure vessel. The filter is normally oriented so that the first end cap may be termed an "upper" end cap and the second end cap a "lower" end cap. While this is the preferred orientation, the filter will function in other orientations.
A tightly wrapped filter media is secured circumferentially around the outer tubular surface of the rigid tubular member and encased in a synthetic sock material. The fuel flows to a filter through a fuel inlet opening of a pressure vessel. The fuel then flows through the synthetic sock and the wrapped filter media and then proceeds into the interior of the fuel pervious rigid tubular member and out the bottom through the openings in the second end cap. The filter media serves to entrap particulate matter, and, in addition, the filter media used in the filter of this disclosure has the characteristics of entrapping water to thereby resist the flow of water through the filter. Further, the filter media is such that as water is entrapped further flow of all fluids through the filter media is resisted. It can be seen that as water is trapped, the pressure drop required to force fluid through the filter media increases at a rate directly proportional to the quantity of water intercepted by the filter media.
A tubular retention sleeve having an opening therethrough and having a modified inside diameter is concentrically affixed to the first end cap and extends down a short distance through the rigid tubular member. This mechanism is positioned upstream or opposite the second end cap. Positioned internal to the cylindrical sleeve, initially in a free floating state, is a ball formed of plastic material. When fuel flow is introduced to the filter, differential pressure will seat the ball within the modified inside diameter of the tubular sleeve. The ball is held in normal engagement with the sleeve so as to prevent fuel flow therethrough. The tubular retention sleeve is of a deformable material, such as aluminum or stiff plastic.
At the opposite end the fuel outlet end, the filter media and tubular member are affixed to the second end cap. The second end cap is formed in such a manner as to provide an annular seal for the ball to seal against.
As hydrocarbon fuel, such as jet fuel or diesel fuel, flows through the filter, the filter media intercepts any entrained particulate matter. The pressure drop across the filter does not significantly increase as long as the fluid flowing is substantially all hydrocarbon fuel. However, any water that is commingled with the fuel is entrapped or absorbed by the filter media. This action restricts further fluid flow through the filter. As more water is absorbed, the pressure differential necessary for further fuel to pass therethrough increases. When this pressure differential develops above a preselected level, the pressure differential across the ball forces the sleeve to deform and pass through the tubular retention sleeve. The ball then enters into the interior of the rigid tubular member and passes to the opposite end thereof where it encounters the circumferential sealing surface within the second end cap. This results in blockage of all further flow through the filter.
A significant improvement of the present invention is the initial free floating position of the valve ball. This condition eliminates any requirement of a predetermined or prepressed condition within the inside diameter of ball retainer thus eliminating the possibility of error by human factor. Sizing of the ball retention seat at the closed end of the retention sleeve can be based on acceleration generated by fluid flow (GPM) relative to the diameter of the ball retention seat and the deformation factor of the retention sleeve.
For another prior art showing of a fuel filter with positive water shutoff see U.S. Pat. No. 4,959,141 issued to Robert D. Anderson on Sep. 25, 1990.